The present invention refers to a centrifugal pump for fluids containing large or long solid objects. Primarily this means wooden chips, textile- and fibre parts, plastic and other solid pieces in the size order of 5-150 mm. Pumps according to the invention are especially intended for pumping of liquid which has a large content of solid material which may be up to about 50%.
Solid objects cause problems when pumping with centrifugal pumps in that they both stick on the edges of the vanes of the pump wheel and force their way in between the pump wheel and the housing and get stuck to either one of these where they may cause the pump wheel to slow down or get stuck. The larger objects may also bridge between two vanes. Objects which have stuck and rotate together with the pump wheel easily gather more objects and the aggregate often grows rapidly. In all cases the flow through the pump is disturbed and its capacity is reduced. When such problems occur the pump has to be stopped and cleaned which often brings with it a stop for the entire process in which the pump is included.
The present invention is for a centrifugal pump in which the above mentioned drawbacks are avoided. The object of the present invention is a pump of the above mentioned kind such that as far as possible it is avoided that solid objects stick to the pump wheel or housing. It is another object of the invention to achieve release of stuck objects as soon as possible without having to stop the pump or take any other special action.